RESUMO
Glycosylation is one of the most structurally and functionally diverse co- and post-translational modifications in a cell. Addition and removal of glycans, especially to proteins and lipids, characterize this process which has important implications in several biological processes. In mammals, the repeated enzymatic addition of a sialic acid unit to underlying sialic acids (Sia) by polysialyltransferases, including ST8Sia2, leads to the formation of a sugar polymer called polysialic acid (polySia). The functional relevance of polySia has been extensively demonstrated in the nervous system. However, the role of polysialylation in infection is still poorly explored. Previous reports have shown that Trypanosoma cruzi (T. cruzi), a flagellated parasite that causes Chagas disease (CD), changes host sialylation of glycoproteins. To understand the role of host polySia during T. cruzi infection, we used a combination of in silico and experimental tools. We observed that T. cruzi reduces both the expression of the ST8Sia2 and the polysialylation of target substrates. We also found that chemical and genetic inhibition of host ST8Sia2 increased the parasite load in mammalian cells. We found that modulating host polysialylation may induce oxidative stress, creating a microenvironment that favors T. cruzi survival and infection. These findings suggest a novel approach to interfere with parasite infections through modulation of host polysialylation.
Assuntos
Doença de Chagas , Ácidos Siálicos , Sialiltransferases , Trypanosoma cruzi , Trypanosoma cruzi/genética , Trypanosoma cruzi/enzimologia , Trypanosoma cruzi/fisiologia , Sialiltransferases/metabolismo , Sialiltransferases/genética , Doença de Chagas/parasitologia , Ácidos Siálicos/metabolismo , Humanos , Animais , GlicosilaçãoRESUMO
Gastric cancer (GC) is one of the leading causes of cancer-related deaths worldwide. Despite progress in the last decades, there are still no reliable biomarkers for the diagnosis of and prognosis for GC. Aberrant sialylation is a widespread critical event in the development of GC. Neuraminidases (Neu) and sialyltransferases (STs) regulate the ablation and addition of sialic acid during glycoconjugates biosynthesis, and they are a considerable source of biomarkers in various cancers. This study retrospectively characterized Neu3 and ST3Gal3 expression by immunohistochemistry in 71 paraffin-embedded GC tissue specimens and analyzed the relationship between their expression and the clinicopathological parameters. Neu3 expression was markedly increased in GC tissues compared with non-tumoral tissues (p<0.0001). Intratumoral ST3Gal3 staining was significantly associated with intestinal subtype (p=0.0042) and was negatively associated with angiolymphatic invasion (p=0.0002) and higher histological grade G3 (p=0.0066). Multivariate analysis revealed that ST3Gal3 positivity is able to predict Lauren's classification. No associations were found between Neu3 staining and clinical parameters. The in silico analysis of mRNA expression in GC validation cohorts corroborates the significant ST3Gal3 association with higher histological grade observed in our study. These findings suggest that ST3Gal3 expression may be an indicator for aggressiveness of primary GC.
Assuntos
Neoplasias Gástricas , Humanos , Ácido N-Acetilneuramínico , RNA Mensageiro , Estudos Retrospectivos , Sialiltransferases/genética , Sialiltransferases/metabolismo , Neoplasias Gástricas/patologiaRESUMO
Gangliosides are glycosphingolipids abundantly expressed in the vertebrate nervous system, and are classified into a-, b-, or c-series according to the number of sialic acid residues. The enzyme GD3 synthase converts GM3 (an a-series ganglioside) into GD3, a b-series ganglioside highly expressed in the developing and adult retina. The present study evaluated the visual system of GD3 synthase knockout mice (GD3s-/- ), morphologically and functionally. The absence of b- series gangliosides in the retinas of knockout animals was confirmed by mass spectrometry imaging, which also indicated an accumulation of a-series gangliosides, such as GM3. Retinal ganglion cell (RGC) density was significantly reduced in GD3s-/- mice, with a similar reduction in the number of axons in the optic nerve. Knockout animals also showed a 15% reduction in the number of photoreceptor nuclei, but no difference in the bipolar cells. The area occupied by GFAP-positive glial cells was smaller in GD3s-/- retinas, but the number of microglial cells/macrophages did not change. In addition to the morphological alterations, a 30% reduction in light responsiveness was detected through quantification of pS6-expressing RGC, an indicator of neural activity. Furthermore, electroretinography (ERG) indicated a significant reduction in RGC and photoreceptor electrical activity in GD3s-/- mice, as indicated by scotopic ERG and pattern ERG (PERG) amplitudes. Finally, evaluation of the optomotor response demonstrated that GD3s-/- mice have reduced visual acuity and contrast sensitivity. These results suggest that b-series gangliosides play a critical role in regulating the structure and function of the mouse visual system.
Assuntos
Sensibilidades de Contraste/fisiologia , Deleção de Genes , Retina/enzimologia , Sialiltransferases/deficiência , Sialiltransferases/genética , Acuidade Visual/fisiologia , Animais , Eletrorretinografia/métodos , Feminino , Masculino , Camundongos , Camundongos da Linhagem 129 , Camundongos Knockout , Estimulação Luminosa/métodosRESUMO
Altered expression of miR-182 has been observed in various types of human cancer. The purpose of this study was to investigate the expression of miR-182 and its role in prostate cancer (PCa). Expression of miR-182 and ST6GALNAC5 in tumor tissues and the Du145 PCa cell line was analyzed. Cell proliferation assay, colony formation assay, transwell assay, and wound healing assay were performed. The impact of miR-182 on tumor growth was investigated using a xenograft model. The results indicated that expression of miR-182 was higher in PCa tissues and cell lines, while ST6GALNAC5 was decreased. Downregulating miR-182 significantly inhibited the capacities of proliferation and invasion of PC3 and Du145 cells. ST6GALNAC5 was demonstrated to be a target of miR-182 by luciferase assay, and western blot results indicated PI3K/Akt pathway was involved in miR-182 associated effects on PC3 and Du145 cells. The animal experiment suggested that knockdown of miR-182 inhibited tumor growth. Our study proved that miR-182 participated in the proliferation and invasion of PCa cells via mediating expression of ST6GALNAC5 and established a miR-182/ST6GALNAC5/PI3K/AKT axis in regulation of tumor progression. Our investigation provided a basis for further exploration of the application of miR-182 or ST6GALNAC5-associated therapies for PCa patients.
Assuntos
MicroRNAs , Neoplasias da Próstata , Animais , Linhagem Celular Tumoral , Movimento Celular , Proliferação de Células , Regulação Neoplásica da Expressão Gênica , Humanos , Masculino , MicroRNAs/genética , Fosfatidilinositol 3-Quinases , Neoplasias da Próstata/genética , SialiltransferasesRESUMO
Polysialic acid (polySia) is a highly regulated polymer of sialic acid (Sia) with such potent biophysical characteristics that when expressed drastically influences the interaction properties of cells. Although much of what is known of polySia in mammals has been elucidated from the study of its role in the central nervous system (CNS), polySia is also expressed in other tissues, including the immune system where it presents dynamic changes during differentiation, maturation, and activation of different types of immune cells of the innate and adaptive response, being involved in key regulatory mechanisms. At least six polySia protein carriers (CCR7, ESL-1, NCAM, NRP2, ST8Sia 2, and ST8Sia 4) are expressed in different types of immune cells, but there is still much to be explored in regard not only to the regulatory mechanisms that determine their expression and the structure of polySia chains but also to the identification of the cis- and trans- ligands of polySia that establish signaling networks. This review summarizes the current knowledge on polySia in the immune system, addressing its biosynthesis, its tools for identification and structural characterization, and its functional roles and therapeutic implications.
Assuntos
Moléculas de Adesão de Célula Nervosa , Sialiltransferases , Animais , Sistema Imunitário/metabolismo , Mamíferos/metabolismo , Moléculas de Adesão de Célula Nervosa/metabolismo , Ácidos Siálicos/metabolismo , Sialiltransferases/genética , Sialiltransferases/metabolismoRESUMO
BACKGROUND: Chemoresistance is the major cause of therapeutic failure in triple negative breast cancer (TNBC). In this work, we investigated the molecular mechanism for the development of TNBC chemoresistance. METHODS: mRNA and protein levels of ST8SIA1 were analyzed in chemosensitive and chemoresistant TNBC cells and tissues. Proliferation and survival assays were performed to determine the role of ST8SIA1 in TNBC chemoresistance. RESULTS: We found that ST8SIA1 mRNA and protein levels were increased in multiple TNBC cell lines after prolonged exposure to chemotherapeutic drugs. Consistently, retrospective study demonstrated that the majority of TNBC patients who developed chemoresistance displayed upregulation of ST8SIA1. We further found that chemoresistant TNBC cells were more sensitive than chemosensitive cells to ST8SIA1 inhibition in decreasing growth and viability. Consistently, ST8SIA1 inhibition augmented the efficacy of chemotherapy in TNBC cells. Mechanism studies demonstrated that ST8SIA1 inhibition led to suppression of FAK/Akt/mTOR and Wnt/ß-catenin signalling pathways. CONCLUSIONS: These findings provide an explanation for the heterogeneity of chemotherapy responses across TNBC individuals and reveal the supportive roles of ST8SIA1in TNBC chemoresistance.
Assuntos
Proteínas Proto-Oncogênicas c-akt , Sialiltransferases/antagonistas & inibidores , Serina-Treonina Quinases TOR , Neoplasias de Mama Triplo Negativas/tratamento farmacológico , Neoplasias de Mama Triplo Negativas/metabolismo , Via de Sinalização Wnt , Antibióticos Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Doxorrubicina/farmacologia , Resistencia a Medicamentos Antineoplásicos , Feminino , Humanos , N-Acetilgalactosaminiltransferases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , RNA Mensageiro/metabolismo , RNA Interferente Pequeno , Estudos Retrospectivos , Sialiltransferases/metabolismo , Serina-Treonina Quinases TOR/metabolismo , Regulação para CimaRESUMO
Altered expression of miR-182 has been observed in various types of human cancer. The purpose of this study was to investigate the expression of miR-182 and its role in prostate cancer (PCa). Expression of miR-182 and ST6GALNAC5 in tumor tissues and the Du145 PCa cell line was analyzed. Cell proliferation assay, colony formation assay, transwell assay, and wound healing assay were performed. The impact of miR-182 on tumor growth was investigated using a xenograft model. The results indicated that expression of miR-182 was higher in PCa tissues and cell lines, while ST6GALNAC5 was decreased. Downregulating miR-182 significantly inhibited the capacities of proliferation and invasion of PC3 and Du145 cells. ST6GALNAC5 was demonstrated to be a target of miR-182 by luciferase assay, and western blot results indicated PI3K/Akt pathway was involved in miR-182 associated effects on PC3 and Du145 cells. The animal experiment suggested that knockdown of miR-182 inhibited tumor growth. Our study proved that miR-182 participated in the proliferation and invasion of PCa cells via mediating expression of ST6GALNAC5 and established a miR-182/ST6GALNAC5/PI3K/AKT axis in regulation of tumor progression. Our investigation provided a basis for further exploration of the application of miR-182 or ST6GALNAC5-associated therapies for PCa patients.
Assuntos
Humanos , Animais , Masculino , Neoplasias da Próstata/genética , MicroRNAs/genética , Sialiltransferases , Regulação Neoplásica da Expressão Gênica , Movimento Celular , Fosfatidilinositol 3-Quinases , Linhagem Celular Tumoral , Proliferação de CélulasRESUMO
Changes in protein levels in different components of the apical junctional complex occur in colorectal cancer (CRC). Claudin3 is one of the main constituents of tight junctions, and its overexpression can increase the paracellular flux of macromolecules, as well as the malignant potential of CRC cells. The aim of this study was to investigate the molecular mechanisms involved in the regulation of claudin3 and its prognostic value in CRC. In silico evaluation in each of the CRC consensus molecular subtypes (CMSs) revealed that high expression levels of CLDN3 (gene encoding claudin3) in CMS2 and CMS3 worsened the patients' longterm survival, whereas a decrease in claudin3 levels concomitant with a reduction in phosphorylation levels of epidermal growth factor receptor (EGFR) and insulinlike growth factor 1 receptor (IGF1R) could be achieved by inhibiting Nglycan biosynthesis in CRC cells. We also observed that specific inactivation of these receptor tyrosine kinases (RTKs) led to a decrease in claudin3 levels, and this regulation seems to be mediated by phospholipase C (PLC) and signal transducer and activator of transcription 3 (STAT3) in CRC cells. RTKs are modulated by their Nlinked glycans, and inhibition of Nglycan biosynthesis decreased the claudin3 levels; therefore, we evaluated the correlation between Nglycogenes and CLDN3 expression levels in each of the CRC molecular subtypes. The CMS1 (MSI immune) subtype concomitantly exhibited low expression levels of CLDN3 and Nglycogenes (MGAT5, ST6GAL1, and B3GNT8), whereas CMS2 (canonical) exhibited high gene expression levels of CLDN3 and Nglycogenes (ST6GAL1 and B3GNT8). A robust positive correlation was also observed between CLDN3 and B3GNT8 expression levels in all CMSs. These results support the hypothesis of a mechanism integrating RTK signaling and Nglycosylation for the regulation of claudin3 levels in CRC, and they suggest that CLDN3 expression can be used to predict the prognosis of patients identified as CMS2 or CMS3.
Assuntos
Antígenos CD/genética , Claudina-3/genética , Neoplasias Colorretais/genética , N-Acetilglucosaminiltransferases/genética , Sialiltransferases/genética , Neoplasias Colorretais/patologia , Intervalo Livre de Doença , Receptores ErbB/genética , Feminino , Regulação Neoplásica da Expressão Gênica/genética , Glicosilação , Humanos , Masculino , Pessoa de Meia-Idade , Prognóstico , Receptor IGF Tipo 1/genética , Fator de Transcrição STAT3/genética , Transdução de Sinais/genéticaRESUMO
BACKGROUND: Brigatinib is a potent ROS1 inhibitor. The existing data on its clinical activity in ROS1-rearranged non-small cell lung cancer (NSCLC) are limited to four cases. METHODS: Six patients with ROS1-rearranged advanced NSCLC treated with brigatinib were identified through search of the internal databases of four participating cancer centers. Four additional patients were selected by PubMed and Google Scholar search. The objective response rate (ORR), progression-free survival (PFS) (RECIST v.1.1), duration of treatment (DOT), and safety were assessed. RESULTS: Of eight patients evaluable for response assessment (crizotinib naive-1, crizotinib resistant -7), three patients demonstrated a partial response (ORR-37%). One crizotinib-naive patient had an ongoing response at 21.6 months. Of seven crizotinib-resistant patients, two patients demonstrated a partial response (ORR-29%), and one patient (14%) had stable disease. PFS, available in four crizotinib-resistant patients, was 7.6 + , 2.9, 2.0, and 0.4 months. In crizotinib-resistant patients, DOT was 9.7 + , 7.7 + , 7.6 + , 4.0, 2.0, 1.1, 0.4 months, and was not reported in two patients. Genomic profiling in one responder revealed no ROS1 alteration, suggesting that the response was attributable to "off-target" brigatinib activity. In two patients with progressive disease, genomic profiling demonstrated a cMET exon 14 mutation + KRAS G12A mutation in one case, and a persisting ROS1-CD74 fusion + TP53 K139N, FGFR2 E250G, ATM G2695D, and NF1 R2258Q mutations in the other. No grade 3-5 toxicity was observed. CONCLUSION: Brigatinib demonstrated modest activity in crizotinib-resistant ROS1-rearranged NSCLC. Its intracranial and systemic activity should be assessed in correlation with the underlying molecular mechanism of crizotinib resistance.
Our series is the first to describe brigatinib activity in ROS1-altered NSCLC. In crizotinib-resistant patients, ORR with brigatinib was 29%. PFS with brigatinib was 7.6+, 2.9, 2.0, and 0.4 months. DOT with brigatinib was 9.7+, 7.7+, 7.6+, 4.0, 2.0, 1.1, 0.4 months. The correlation between response and molecular resistance needs further exploration.
Assuntos
Antineoplásicos/uso terapêutico , Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Crizotinibe/uso terapêutico , Neoplasias Pulmonares/tratamento farmacológico , Compostos Organofosforados/uso terapêutico , Proteínas Tirosina Quinases/genética , Proteínas Proto-Oncogênicas/genética , Pirimidinas/uso terapêutico , Idoso , Idoso de 80 Anos ou mais , Antígenos CD/genética , Institutos de Câncer , Carcinoma Pulmonar de Células não Pequenas/genética , Resistencia a Medicamentos Antineoplásicos , Feminino , Rearranjo Gênico/genética , Genes ras/genética , Humanos , Neoplasias Pulmonares/genética , Masculino , Pessoa de Meia-Idade , Mutação , Proteínas de Fusão Oncogênica , Compostos Organofosforados/efeitos adversos , Intervalo Livre de Progressão , Proteínas Tirosina Quinases/antagonistas & inibidores , Proteínas Proto-Oncogênicas/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-met/genética , Pirimidinas/efeitos adversos , Sialiltransferases/genéticaRESUMO
The ST3GAL4 gene encodes the enzyme Galß1-4GlcNAc α2,3 sialyltransferase (ST3Gal IV). This enzyme participates in the synthesis of the sialyl Lewis x antigen. In different cancer types altered expression of this antigen has been reported. The transcriptional regulation of this gene is very complex, different mRNA variants (V1-V10) have been reported and are originated by the activity of different promoters and alternative splicing. Only the promoter that gives rise to the V3 variant has not been previously reported. The objective of this work was to identify and characterize the V3 promoter of the ST3GAL4 gene. For this, the putative V3 promoter of the ST3GAL4 gene was delimited by in silico analysis. The complete promoter and smaller versions were cloned in a reporter plasmid. The constructs were transfected in the HaCaT cells and the promoter activity was evaluated by luciferase reporter assays. The cloned region showed promoter activity, and the basal activity was not dependent on TATA boxes. However, the GC boxes, an initiator element (Inr) and downstream promoter element (DPE) could contribute to basal activity. The promoter contains several binding sites for the nuclear factor of activated T-cells (NFAT) that could participate in inducible activity during the immune response. The minimal promoter corresponds to a fragment of approximately 300 bp, located in the position -347 b to -40 b. The characterization of the V3 promoter of the ST3GAL4 gene completes the study of the four promoters of this gene, this contributes to the understanding of its complex transcription regulation.
Assuntos
Regiões Promotoras Genéticas , Sialiltransferases/genética , Transcrição Gênica , Processamento Alternativo , Sítios de Ligação , Linhagem Celular , Clonagem Molecular , Biologia Computacional , Humanos , Isoenzimas/genética , Fatores de Transcrição NFATC/metabolismoRESUMO
Gangliosides are constituents of the mammalian cell membranes and participate in the inflammatory response. However, little is known about the presence and enzymatic activity of ganglioside sialyltransferases at the cell surface of macrophages, one of the most important immune cells involved in the innate inflammatory process. In the present study, using biochemical and fluorescent microscopy approaches, we found that endogenous ST8Sia-I is present at the plasma membrane (ecto-ST8Sia-I) of murine macrophage RAW264.7 cells. Moreover, ecto-ST8Sia-I can synthetize GD3 ganglioside at the cell surface in lipopolysaccharide (LPS)-stimulated macrophages even when LPS-stimulated macrophages reduced the total ST8Sia-I expression levels. Besides, cotreatment of LPS with an inhibitor of nitric oxide (NO) synthase recovered the ecto-ST8Sia-I expression, suggesting that NO production is involved in the reduction of ST8Sia-I expression. The diminution of ST8Sia-I expression in LPS-stimulated macrophages correlated with a reduction of GD3 and GM1 gangliosides and with an increment of GD1a. Taken together, the data supports the presence and activity of sialyltransferases at the plasma membrane of RAW264.7 cells. The variations of ecto-ST8Sia-I and ganglioside levels in stimulated macrophages constitutes a promissory pathway to further explore the physiological role of this and others ganglioside metabolism-related enzymes at the cell surface during the immune response.
Assuntos
Membrana Celular/metabolismo , Gangliosídeo G(M1)/metabolismo , Gangliosídeos/metabolismo , Macrófagos/metabolismo , Sialiltransferases/metabolismo , Animais , Células CHO , Linhagem Celular , Cricetulus/metabolismo , Lipogênese/fisiologia , Lipopolissacarídeos/metabolismo , Camundongos , Óxido Nítrico/metabolismo , Células RAW 264.7RESUMO
OBJECTIVE/BACKGROUND: Obstructive sleep apnea (OSA) is a sleep-related breathing disorder that has a complex phenotype. Currently, few genes have been linked with OSA. Thus, the aim of this study was to conduct a genome-wide association study (GWAS) of the apnea-hypopnea index (AHI) variation along time (delta-AHI) in a prospective cohort. METHODS: We used data derived from the São Paulo Epidemiologic Sleep Study (EPISONO) (n = 1074) cohort, which was followed over eight years (n = 712). Our phenotype of interest was delta-AHI and incident OSA. Further, we were interested on the time-dependent effect of genetic variants. Our final GWAS model used delta-AHI as a dependent variable and the SNPs and covariates as independent variables. We also performed a gene-set and pathway analysis. RESULTS: The delta-AHI increased on average 6.1 events/hour (standard deviation = 14.9) over the follow-up. We found two significant and 21 suggestive variants associated with delta-AHI. The strongest association (rs12415421) was observed at ST8SIA6 gene and the other significant hit (rs4731117) was in an intergenic region in linkage disequilibrium with our third hit (rs12669165) in the ASB15 gene. We found an effect of the allele rs12415421 for the OSA incidence. Additionally, we observed that individuals with both risk alleles presented a higher incidence of OSA when compared to those with one or without any risk alleles. CONCLUSIONS: This study has identified genes in these associated regions with delta-AHI, which seem to be involved in growth and stability of muscle and bone. We also observed an effect of both allele frequencies in the incidence of OSA.
Assuntos
Alelos , Estudo de Associação Genômica Ampla , Proteínas/genética , Sialiltransferases/genética , Apneia Obstrutiva do Sono , Adulto , Brasil/epidemiologia , Feminino , Humanos , Incidência , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Polissonografia , Estudos Prospectivos , Apneia Obstrutiva do Sono/epidemiologia , Apneia Obstrutiva do Sono/genética , Fatores de TempoRESUMO
This study investigated the effect of 7-chloro-4-(phenylselanyl) quinoline (4-PSQ) to restore the cognitive impairment caused by aging in male Wistar rats. Moreover, modulation of neuroplasticity markers, acetylcholinesterase (AChE) activity, and cholesterol levels was performed. Aged rats were intragastrically treated with 4-PSQ (5 mg/kg) for 7 days. Animals were tested in behavioral tasks, and then plasma (to determine cholesterol levels), hippocampus, and cerebral cortex (to determine neural cell adhesion molecule (NCAM) and polysialyltransferase (PST) levels, and AChE activity) were removed. Our findings demonstrated that treatment of aged rats with 4-PSQ restored short-term and long-term memories in the object recognition tests. 4-PSQ treatment did not restore exploratory activity (rearings) but partially restored locomotor activity (crossings) reduced by aging in the open-field test. Moreover, the compound restored the reduction in the NCAM and PST levels, and AChE activity in cerebral structures, as well as the increase in the plasma cholesterol levels, caused by aging in rats. In conclusion, 4-PSQ restored cognitive impairment caused by aging in rats by modulating synaptic plasticity, cholinergic system, and cholesterol levels.
Assuntos
Acetilcolinesterase/metabolismo , Colesterol/metabolismo , Memória/efeitos dos fármacos , Plasticidade Neuronal/efeitos dos fármacos , Compostos Organosselênicos/farmacologia , Quinolinas/farmacologia , Animais , Colesterol/sangue , Locomoção/efeitos dos fármacos , Masculino , Moléculas de Adesão de Célula Nervosa/metabolismo , Compostos Organosselênicos/química , Quinolinas/química , Ratos Wistar , Sialiltransferases/metabolismoRESUMO
ST3GAL4 gene expression is altered in different cancer types, including cervical cancer. Several mRNA transcripts have been reported for this gene; however, their expression levels in cervical cancer have not been analyzed. ST3GAL4 encodes for ßgalactosidase α2,3sialyltransferase 4, involved in the biosynthesis of the tumour antigens sLe(x) and sulfosLe(x). The present study evaluated the presence of three mRNA variants (V1, V2 and V3) in cervical cancer cell lines, detecting the three variants. Additionally, the expression level of the V1 transcript of the ST3GAL4 gene was determined by reverse transcriptionquantitative polymerase chain reaction in cervical cell lines and in normal, premalignant and cervical cancer tissue. The V1 transcript of the ST3GAL4 demonstrated significant decreased expression in premalignant and malignant cervical tissues. The results suggested that deregulation of this gene could occur prior to the presence of cancer and demonstrated the importance of evaluating the expression level of V1, and its association with disease progression.
Assuntos
Regulação Neoplásica da Expressão Gênica , Isoformas de RNA/genética , Sialiltransferases/genética , Neoplasias do Colo do Útero/enzimologia , Adolescente , Adulto , Idoso , Progressão da Doença , Feminino , Humanos , Pessoa de Meia-Idade , Neoplasias do Colo do Útero/genética , Adulto JovemRESUMO
PURPOSE: Presence of cancer stem cells (CSCs) contributes to tumor outgrowth, chemo-resistance and relapse in some cancers including colorectal carcinoma (CRC). The current characterization methods of CSCs in CRC only allows enrichment of CSCs but not their purification. Recent reports showed that ST6 beta-galactoside alpha-2,6-sialyltransferase 1 (ST6Gal-I) plays an essential role in protecting tumor cells against harsh environment like oxidative stress and nutrient deprivation. Therefore, whether ST6Gal-I may be highly expressed in CSCs or whether it may enhance resistance of tumor cells to chemotherapy deserves exploration. METHOD: ST6Gal-I levels were determined in CRC specimens, compared to paired normal colorectal tissue, and examined in CD133+ vs CD133- CRC cells, and CD44+ vs CD44- CRC cells. ST6Gal-I levels and their association with patient survival were examined. In vivo, 2 CRC cell lines Caco-2 and SW48 were transduced with two lentiviruses, one lentivirus carrying a green fluorescent protein reporter and a luciferase reporter under a cytomegalovirus promoter to allow tracing tumor cells by both fluorescence and luciferase activity, and one lentivirus carrying a nuclear red fluorescent protein under the control of ST6Gal-I promoter to allow separation of ST6Gal-I+ vs ST6Gal-I- CRC cells. Tumor sphere formation, resistance to fluorouracil-induced apoptosis, and frequency of tumor formation after serial adoptive transplantation were done on ST6Gal-I+ vs ST6Gal-I- CRC cells. RESULT: ST6Gal-I levels were significantly upregulated in clinically obtained CRC specimens, compared to paired normal colorectal tissue. Poorer patient survival was detected in ST6Gal-I-high CRC, compared to ST6Gal-I-low subjects. Higher levels of ST6Gal-I were detected in CD133+ CRC cells than CD133- CRC cells, and in CD44+ CRC cells than in CD44- CRC cells. Compared to ST6Gal-I- CRC cells, ST6Gal-I+ CRC cells generated significantly more tumor spheres in culture, were more resistant to fluorouracil-induced apoptosis likely through upregulating cell autophagy, and generated tumor more frequently after serial adoptive transplantation. CONCLUSION: ST6Gal-I may be highly expressed in the cancer stem-like cells in CRC and enhances cancer cell resistance to chemotherapy.
Assuntos
Neoplasias Colorretais/tratamento farmacológico , Células-Tronco Neoplásicas/enzimologia , Sialiltransferases/metabolismo , Linhagem Celular Tumoral , Neoplasias Colorretais/enzimologia , Neoplasias Colorretais/mortalidade , Neoplasias Colorretais/patologia , Resistencia a Medicamentos Antineoplásicos , Humanos , beta-D-Galactosídeo alfa 2-6-SialiltransferaseRESUMO
Ganglioside glycosyltransferases (GGTs) are type II membrane proteins bearing a short N-terminal cytoplasmic tail, a transmembrane domain (TMD), and a lumenal catalytic domain. The expression and activity of these enzymes largely determine the quality of the glycolipids that decorate mammalian cell membranes. Many glycosyltransferases (GTs) are themselves glycosylated, and this is important for their proper localisation, but few if any other post-translational modifications of these proteins have been reported. Here, we show that the GGTs, ST3Gal-V, ST8Sia-I, and ß4GalNAcT-I are S-acylated at conserved cysteine residues located close to the cytoplasmic border of their TMDs. ST3Gal-II, a GT that sialylates glycolipids and glycoproteins, is also S-acylated at a conserved cysteine located in the N-terminal cytoplasmic tail. Many other GTs also possess cysteine residues in their cytoplasmic regions, suggesting that this modification occurs also on these GTs. S-acylation, commonly known as palmitoylation, is catalysed by a family of palmitoyltransferases (PATs) that are mostly localised at the Golgi complex but also at the endoplasmic reticulum (ER) and the plasma membrane. Using GT ER retention mutants, we found that S-acylation of ß4GalNAcT-I and ST3Gal-II takes place at different compartments, suggesting that these enzymes are not substrates of the same PAT. Finally, we found that cysteines that are the target of S-acylation on ß4GalNAcT-I and ST3Gal-II are involved in the formation of homodimers through disulphide bonds. We observed an increase in ST3Gal-II dimers in the presence of the PAT inhibitor 2-bromopalmitate, suggesting that GT homodimerisation may be regulating S-acylation.
Assuntos
N-Acetilgalactosaminiltransferases/metabolismo , Processamento de Proteína Pós-Traducional , Sialiltransferases/metabolismo , Acilação , Sequência de Aminoácidos , Animais , Células CHO , Linhagem Celular , Sequência Conservada , Cricetulus , Cisteína/metabolismo , Dimerização , Humanos , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Microscopia de Fluorescência , Mutação , N-Acetilgalactosaminiltransferases/química , N-Acetilgalactosaminiltransferases/genética , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/metabolismo , Filogenia , Domínios e Motivos de Interação entre Proteínas , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/metabolismo , Sialiltransferases/química , Sialiltransferases/genética , beta-Galactosídeo alfa-2,3-SialiltransferaseRESUMO
ST6GalNAc-I, the sialyltransferase responsible for sialyl-Tn (sTn) synthesis, has been previously reported to be positively associated with cancer aggressiveness. Here we describe a novel sTn-dependent mechanism for chemotherapeutic resistance. We show that sTn protects cancer cells against chemotherapeutic-induced cell death by decreasing the interaction of cell surface glycan receptors with galectin-3 and increasing its intracellular accumulation. Moreover, exogenously added galectin-3 potentiated the chemotherapeutics-induced cytotoxicity in sTn non-expressing cells, while sTn overexpressing cells were protected. We also found that the expression of sTn was associated with a reduction in galectin-3-binding sites in human gastric samples tumors. ST6GalNAc-I knockdown restored galectin-3-binding sites on the cell surface and chemotherapeutics sensibility. Our results clearly demonstrate that an interruption of O-glycans extension caused by ST6GalNAc-I enzymatic activity leads to tumor cells resistance to chemotherapeutic drugs, highlighting the need for the development of novel strategies to target galectin-3 and/or ST6GalNAc-I.
Assuntos
Antineoplásicos/farmacologia , Cisplatino/farmacologia , Resistencia a Medicamentos Antineoplásicos , Galectina 3/metabolismo , Neoplasias Gástricas/tratamento farmacológico , Animais , Antígenos Glicosídicos Associados a Tumores/genética , Antígenos Glicosídicos Associados a Tumores/metabolismo , Proteínas Sanguíneas , Linhagem Celular Tumoral , Proliferação de Células , Relação Dose-Resposta a Droga , Galectinas , Glicosilação , Humanos , Camundongos Endogâmicos BALB C , Camundongos Nus , Processamento de Proteína Pós-Traducional , Transporte Proteico , Interferência de RNA , Sialiltransferases/genética , Sialiltransferases/metabolismo , Neoplasias Gástricas/genética , Neoplasias Gástricas/metabolismo , Neoplasias Gástricas/patologia , Fatores de Tempo , Transfecção , Carga TumoralRESUMO
Cell surface of eukaryotic cells is covered with a wide variety of sialylated molecules involved in diverse biological processes and taking part in cell-cell interactions. Although the physiological relevance of these sialylated glycoconjugates in vertebrates begins to be deciphered, the origin and evolution of the genetic machinery implicated in their biosynthetic pathway are poorly understood. Among the variety of actors involved in the sialylation machinery, sialyltransferases are key enzymes for the biosynthesis of sialylated molecules. This review focus on ß-galactoside α2,3/6-sialyltransferases belonging to the ST3Gal and ST6Gal families. We propose here an outline of the evolutionary history of these two major ST families. Comparative genomics, molecular phylogeny and structural bioinformatics provided insights into the functional innovations in sialic acid metabolism and enabled to explore how ST-gene function evolved in vertebrates.
Assuntos
Sialiltransferases/metabolismo , Vertebrados/metabolismo , Animais , Ácido N-Acetilneuramínico/metabolismo , Filogenia , Sialiltransferases/classificação , Sialiltransferases/genética , Vertebrados/genéticaRESUMO
Different host genetic variants may be related to the virulence and transmissibility of pandemic Influenza A(H1N1)pdm09, influencing events such as binding of the virus to the entry receptor on the cell of infected individuals and the host immune response. In the present study, two genetic variants of the ST3GAL1 gene, which encodes the Siaα2-3Galß1- receptor to which influenza A(H1N1)pdm09 virus binds for entry into the host cell, were investigated in an admixed Brazilian population. First, the six exons encoding the ST3GAL1 gene were sequenced in 68 patients infected with strain A(H1N1)pdm09. In a second phase of the study, the rs113350588 and rs1048479 polymorphisms identified in this sample were genotyped in a sample of 356 subjects from the northern and northeastern regions of Brazil with a diagnosis of pandemic influenza. Functional analysis of the polymorphisms was performed in silico and the influence of these variants on the severity of infection was evaluated. The results suggest that rs113350588 and rs1048479 may alter the function of ST3GAL1 either directly through splicing regulation alteration and/or indirectly through LD with SNP with regulatory function. In the study the rs113350588 and rs1048479 polymorphisms were in linkage disequilibrium in the population studied (D' = 0.65). The GC haplotype was associated with an increased risk of death in subjects with influenza (OR = 4.632, 95% CI = 2.10;1.21). The AT haplotype was associated with an increased risk of severe disease and death (OR = 1.993, 95% CI = 1.09;3.61 and OR 4.476, 95% CI = 2.37;8.44, respectively). This study demonstrated for the first time the association of ST3GAL1 gene haplotypes on the risk of more severe disease and death in patients infected with Influenza A(H1N1)pdm09 virus.
Assuntos
Vírus da Influenza A Subtipo H1N1 , Influenza Humana/genética , Polimorfismo de Nucleotídeo Único , Sialiltransferases/genética , Adolescente , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Brasil/epidemiologia , Criança , Pré-Escolar , Comorbidade , Feminino , Predisposição Genética para Doença , Genótipo , Haplótipos/genética , Humanos , Lactente , Influenza Humana/complicações , Influenza Humana/epidemiologia , Influenza Humana/etnologia , Desequilíbrio de Ligação , Masculino , Pessoa de Meia-Idade , Grupos Raciais/genética , Risco , Síndrome Respiratória Aguda Grave/etiologia , Síndrome Respiratória Aguda Grave/mortalidade , Índice de Gravidade de Doença , Adulto Jovem , beta-Galactosídeo alfa-2,3-SialiltransferaseRESUMO
ST3Gal-II, a type II transmembrane protein, is the main mammalian sialyltransferase responsible for GD1a and GT1b ganglioside biosynthesis in brain. It contains two putative N-glycosylation sites (Asn(92) and Asn(211)). Whereas Asn(92) is only conserved in mammalian species, Asn(211) is highly conserved in mammals, birds and fish. The present study explores the occupancy and relevance for intracellular trafficking and enzyme activity of these potential N-glycosylations in human ST3Gal-II. We found that ST3Gal-II distributes along the Golgi complex, mainly in proximal compartments. By pharmacological, biochemical and site-directed mutagenesis, we observed that ST3Gal-II is mostly N-glycosylated at Asn(211) and that this co-translational modification is critical for its exit from the endoplasmic reticulum and proper Golgi localization. The individual N-glycosylation sites had different effects on ST3Gal-II enzymatic activity. Whereas the N-glycan at position Asn(211) seems to negatively influence the activity of the enzyme using both glycolipid and glycoprotein as acceptor substrates, the single N-glycan mutant at Asn(92) had only a moderate effect. Lastly, we demonstrated that the N-terminal ST3Gal-II domain containing the cytosolic, transmembrane and stem region (amino acids 1-51) is able to drive a protein reporter out of the endoplasmic reticulum and to retain it in the Golgi complex. This suggests that the C-terminal domain of ST3Gal-II depends on N-glycosylation to attain an optimum conformation for proper exit from the endoplasmic reticulum, but it does not represent an absolute requirement for Golgi complex retention of the enzyme.